#include <iostream>
#include <vector>
#include <algorithm>
#include <math.h>
#include <map>

#define ALL(x) (x).begin(),(x).end()
#define RALL(x) (x).rbegin(),(x).rend()
#define REP(i,a,n) for(int i = (a);i < (n);i++)
#define PI 3.14159265359
#define MOD 1000000007

using namespace std;

int main(){
    string a,b,ans = "OK\n";
    cin >> a >> b;
    REP(i, 0, a.length()){
        if('A' <= a[i])ans = "NG\n";
    }
    REP(i, 0, b.length()){
        if('A' <= b[i])ans = "NG\n";
    }
    if(a.length() != 1 && a[0] == '0')ans = "NG\n";
    if(b.length() != 1 && b[0] == '0')ans = "NG\n";
    string s = "12345";
    if(a.length() == 5){
        REP(i, 0, 5){
            if(a[i] > s[i])ans = "NG\n";
        }
    }
    if(b.length() == 5){
        REP(i, 0, 5){
            if(b[i] > s[i])ans = "NG\n";
        }
    }
    cout << ans;
    return 0;
}